Gaseous glow-discharge indicator system

ABSTRACT

A gaseous glow indicator tube in which there is contained a plurality of indicator units of a first type and additional indicator units of different types, the anodes and cathodes of all units lying in a common plane, the anodes being energized on a time sequential basis, corresponding cathode segments of each indicator unit being connected to a common energizing lead, whereby only those segments are caused to glow which have their associated anodes energized and which are energized through their respective cathode leads. The cathode segments of at least one of the additional indicator units having a smaller area than that of the cathode segments of the first type indicator unit. The additional type indicator units being particularly designed to indicated exponents, &#39;&#39;&#39;&#39;overflow&#39;&#39;&#39;&#39; and other functions being performed.

Unite States Patet 11 1 Yanagisawa Dec. 17, 1974 [54] GASEOUSGLOW-DISCHARGE INDICATOR 3,435,270 3/1969 Vodicka 313/1095 3,573,5324/1971 Boucher 3l3/109.5 SYSTEM 3,588,571 6/1971 Vemura et 211....313/1095 n t Yuzuru Yanagisawa, Fujisawa, 3,641,383 2/1972 Tagawa313/1095 Japan 3,641,390 2/1972 Nakamura 315/169 R 3,679,933 71972 N'kdt'l .315169RX [73] Asslgnee: Sony Corporation, Tokyo, Japan I d a a e dl [22] Filed: June 27, 1973 Primary ExaminerPalmer C. Demeo Attorney,Agent, or Firm-Hill, Gross, Simpson, Van [21] Appl' 374l33 Santen,Steadman, Chiara & Simpson Related US. Application Data [63]Continuation of Ser. No. 172,855, Aug. 18, 1971, [57] ABSTRACT vabandoned A gaseous glow indicator tube in which there is contained aplurality of indicator units of a first type and [30] Forelgn ApphcatmnPnonty Data additional indicator units of different types, the an- Sept.1,1970 Japan 45-87014 odes and cathodes of all units lying in a commonApr, 26, 1971 Japan 46-27396 plane, the anodes being energized on a timesequential basis, corresponding cathode segments of each indica- 52] us.c1 315/169 TV, 313/517 tor unit being connected to a common energizinglead, [51 Int. Cl 1101 61/66, HOSb 41/38 whereby only those segments areCaused to glow [58] Field 01' Search 313/1095, 210, 220; which havetheir associated anodes energized and 315/169 R, 169 T 58 which areenergized through their respective cathode leads. The cathode segmentsof at least one of the ad- [56] References Cmd ditional indicator unitshaving a smaller area than that UNITED STATES PATENTS of the cathodesegments of the first type indicator 2,735,038 2/1956 Hancock 313/1095 xunit- The additional yp indicator units being P 3,187,320 6/1965 Kupsky313/1095 UX larly designed to indicated exponents, overflow and3,231,776 1/1966 Britnell et ul. 313/1095 other functions beingperformed. 3,289,198 11/1966 Dickson, Jr. et a1 313/1095 UX 3,327,1546/1967 Bowerman 313 1095 9 Claims, 5 Drflwmg Figures fzea PATEN'i'ED 0E0i "x mm :1 855 500 SHEET 10F 2 55 Z: J J 50 w; m w Mm /0 1 ii ri 05$ /3/6 g g m M J x /2 C/ILCULA701Q MA [IQ/ I N VEN TOR 702 we a xv/ma/smm BYATTORNEYS GASEOUS GLOW-DISCHARGE INDICATOR SYSTEM This is acontinuation, of application Ser. No. 172,855, filed Aug. 18, 1971, andnow abandoned.

CROSS REFERENCE TO RELATED APPLICATIONS The present invention is animprovement over the invention disclosed in pending application, Ser.No. 128,888, filed Mar. 29, 1971, and it is also an improvement over theinvention disclosed in Ser. No. 155,555, filed June 22, 197], now U.S.Pat. No. 3,728,571, both of which are assigned to the same assignee asthe present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates in general to gaseous glow indicator tubes and particularly tothat type of indicator tube in which a number of indicator units arecontained within a sealed envelope and which have one or more anodes foreach indicator unit and a number of cathodes for each indicator unit,the anodes being energized on a time sequential basis, and the cathodesbeing connected to a potential source which is negative with respect tothe anode potential source.

2. Description of the Prior Art Gaseous glow indicator tubes whichinclude a plurality of indicator units mounted inside a transparentenvelope and which are utilized for displaying numerals, symbols,letters, or the like, have been commercially available. For example,such indicators have been used with electronic counters and variousother indicating means. One example of such indicators are the socalled"Nixie" tubes in which an anode electrode and a plurality of cathodeelectrodes are aligned in a stack one above the other such that selectedcathode elements may be energized so that an observer sees a selectednumeral or letter. Other glow indicator tubes utilize cathode segmentsmounted in a common plane with an anode in the form of a wire screen ormesh mounted in a second plane and which when various cathode segmentsare energized at the same time that the corresponding anode is energizedthe unit will glow.

Such prior art indicator tubes utilized a separate lead for each of theanodes, or alternatively provide separate leads for each of the cathodesegments. This resulted in indicator tubes with a very large number ofleads and limited the minimum size of the unit as well as requiring manyelectrical connections to be made to each of the units.

In U.S. Pat. No. 3,588,571 an indicator tube is described in which eachof the cathode electrodes or a plurality of indicating units arecommonly connected to each other by a single lead. This eliminates thenecessity for a number of cathode leads corresponding to the number ofcathodes in the entire indicator tube.

SUMMARY OF THE INVENTION In the tubes above referred to, no means wasprovided to indicate an over-flow or to indicate other operationalfunctions which should be brought to the attention of the operator.

The present invention comprises a gaseous glow indicator tube having anumber of indicator units in which the cathode and anode elements areformed in a common plane and wherein the associated cathode segments ofeach of the indicating units are electrically connected together and aresimultaneously energized and in which the anode segments for separateindicating units are time sequentially energized such that a particularindicating unit which has its anode energized produces an indication.Such a tube of this invention has at least one additional indicatingunit in which the cathode and anode elements are formed in a commonplane, and each of the cathode elements has a smaller area than that ofeach of the cathode elements of the indicating units.

Accordingly, one of the objects of this invention is to provide animproved gaseous glow indicator tube in which there is a plurality ofindicator units, an additional plurality of indicator units of differenttypes, at least some of said additional indicator units providing anindication of a function being carried out by the apparatus with whichthe indicator tube is associated.

Another object of the present invention is to provide a novel gaseousglow indicator tube in which a plurality of indicating units and atleast one additional'unit are accommodated therein.

Still another object of the present invention is to provide a gaseousglow indicator tube in which there is contained a plurality of indicatorunits of a first type and at least one indicator unit of a differenttype, the additional indicator unit having an indicating area which issmaller than the indicating area of each of the first type indicatorunits, whereby the glow from the additional indicator unit is brighterthan the glow from the first type indicator units.

A further object of this invention is to provide a gaseous glowindicator tube in which a plurality of indicat BRIEF DESCRIPTION OF THEDRAWINGS FIG. 1 is a plane view of an assembled gaseous glow indicatortube embodying the novel features of the present invention, the centersection of which has been broken away;

FIG. 2 is a sectional view of the gaseous glow indicator tube of FIG. 1showing only the supporting base, the enclosing envelope, the insulatinglayer and an indicating unit;

FIG. 3 is a schematic wiring diagram of the gaseous glow indicator tubeof this invention illustrating the electrical connections between thecathode elements and anode elements of two of the indicator units andillustrating the cathode and anode elements of a functioning indicatorunit;

FIG. 4 is a diagrammatic view of a modified form of indicator tubewhich, in addition to displaying a number of digits, also is able todisplay a times sign, exponents and also functional operation;

FIG. 5 is a schematic wiring diagram of the gaseous glow indicator tubeshown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 diagrammaticallyillustrates a gaseous glow indicator tube 10. This indicator tube 10, asshown in FIG. 2, includes a plate or base 1 1 formed of insulatingmaterial such, for example, as glass. Disposed on the base 11 is a stripof insulating material 13, on which in turn are formed the indicatingunits 16, including both the cathodes and the anodes, as hereinafterwill be explained. The insulating layer 13, as well as the indicatingunits 16 are enclosed by a transparent glass cover 12 which is sealed tothe base 11. The chamber enclosed by the glass cover 12 is filled with asuitable ionizing gas.

Referring back to FIG. 1, the indicating units 16 are made up of a largenumber of indicia diagrammatically shown as 16a, 16b, 16p.

As presently will be explained, each indicating unit 16 is made up of aplurality of anodes and a plurality of cathode segments and provides anindication. It is, of course, necessary to apply a potential between acathode segment and its associated anode, it being understood that thecathode will be negative with respect to the anode. To accomplish this,leads must come out from the indicator tube envelope 12, and such leadsare shown as leads 17 to 37 in FIG. 1.

As will be more fully appreciated by referring to FIG. 3, each of theindicator units 16a to 16p is formed of eight cathode segments that areinsulated from each other and two anode segments. In the presentinvention all of the corresponding cathode segments are electricallyconnected together. The individual indicator units have a pair of anodeelements which are electrically connected together and which areindependently energized so that at a particular time on the particularindicator unit which has its pair of anode elements energized, willglow. Thus, even though the corresponding cathode segments of all of theindicator units 16a to 16p are energized, only the particular indicatorunit which has its anodes energized will glow. The cathode segments andanode segments are formed in a common plane parallel with the plane ofthe layer 13 on which they are formed. Another advantage of the presentinvention lies in the fact that all of the anode and cathode units liein a common plane allow a glow tube to be constructed that is very thinand compact.

As shown in FIG. 3, each of the indicator units 16a to 16p is formed ofeight cathode segments designated by numerals, 46 to 53, respectively.The segments are arranged to form a figure 8 with the decimal segment 53at the lower right hand corner. For example, segments 46, 48 and 50 areabove each other and horizontal as viewed in FIG. 3. Segments 47, 49, 51and 52 are generally vertical as viewed in FIG. 3.

Anode segments 54 and 55 are mounted, respectively. between cathodesegments 48, 49, 50 and 51, and cathode segments 46, 47, 48 and 52.Eight cathode energizing leads 38 to 41 and 43 to 46 extend generallyhorizontally on the insulating plate 11 with the leads 38 to 41 mountedadjacent the upper edge of indicator units 16a to 16p and cathode leads43 to 46 mounted adjacent the lower edge of the indicator units 16a to16p. These may be formed by any well known printed circuit technique.

As shown in H6. 2, the insulating layer 13 is mounted on the glass plate11, and the cathode and anode segments 46 to 55 are formed on layer 13.The fact that both layer 13 and plate 11 are of insulating materialenables the electrical connections to be made to the cathode and anodesegments without any portions being shorted out.

As shown in FIG. 3, cathode lead 38 is connected by conductors 64 toeach cathode segment 51 of all of the indicator units. At the crossingpoints of leads 64 with leads 39, 40 and 41, the insulating layer 13provides separation and insulation. Thus, the leads 64 may be placed onone side of the insulation layer 13 and openings are formed in theinsulation layer 13 and connections are made to the respective segmentsthrough such openings.

Leads 63 connect lead 39 to each of the cathode segments 52 of theindicator units. Leads 61 connect each of the cathode segments 46 to theconductor 40. Leads 62 connect each of the cathode segments 48 to lead41.

Leads 69 connect cathode segments 53 to lead 43. Leads 68 connect eachof the cathode segments 49 to the lead 44. Leads 66 connect each of thecathode segments 50 to the lead 46. Leads 67 connect each of the cathodesegments 47 to lead 45.

Lead 71 connects the two anode segments 54 and 55 of the first indicatorunit 16a to the movable contact of switch Sa.

Lead 76 connects the two anode segments 54' and 55 of the secondindicator unit 16b to the movable contact of a switch Sb.

Each of the anode segments 54 and 55 for a particular indicator unit areelectrically connected together, but the anode segments for differentindicator units are connected to a different switch Sa to Sp throughleads 71, 76, etc., as shown in FIG. 3.

A battery E exemplifies a source of potential and has its negativeterminal connected to ground and its positive terminal connected to theother terminals of the switches Sa to Sp for selectively applying apositive potential to the anode segment of the indicator units, thepositive potential being sufficient to cause the adjacent activatedcathode segments to glow.

The cathode leads 38 to 41 and 43 to 46 are connected to a calculatormatrix 72 as shown in FIG. 3.

A plurality of push buttons 73 are mounted on the calculator matrix 72and may be depressed for indicating a numeral between 0-9. For example,if the numeral 7 is selected, the cathode segments 46, 47 and 49 of allthe indicator units 16a to 16p will be simultaneously energized but onlythe particular indicator unit which has its anode segments 54 and 55energized by the closing of one of the switches Sa to Sp will producethe number 7. Thus, for example, if switch Sb is closed thus applying apositive voltage to the anode segments 54' and 55 of unit 16b from thebattery E, simultaneously when the cathode segments 46' and 47' and 49'are connected to a potential negative with respect to the anodepotential from the calculator matrix 72, the indicator unit 16b willglow and the numeral 7 will be visible.

It is to be realized. of course, that the indicator units are energizedon a time-sharing basis and the switches S0 to Sp may form a portion ofthe calculator matrix 72 and be selectively closed in synchronism withenergization of the cathode segments such that the indicator 10 producesthe desired indication. Techniques for connecting suitable energizingvoltages in a time-sharing manner are known by those skilled in the art.

The indicator tube 10 of this invention, further provides an additionalindicating unit (FIG. 3) on the insulating layer 13 to indicate afunctional sign for the indicating units 16a to 16p. As shown in FIG. 3,the additional indicating unit 80 comprises five cathode segments 81 to85 and six anode segments 86 to 91. The cathode segment 81 is connectedto the lead 40 by a lead 92, the cathode segment 82 is connected to thelead 38 by a lead 93, the cathode segment 83 is connected to the lead 41by a lead 94, the cathode segment 84 is connected to the lead 45 by alead 95 and the cathode segment 85 is connected to the lead 44 by a lead96. The anode segments 86 to 91 are commonly connected with each otherby a lead 97 and this lead 97 is connected to a switch S which isconnected to the battery E.

As clearly shown in FIG. 3, the indicating area of the cathode segmentof each indicating unit 16a to 16p is designed substantially the same,however, the indicating area of the cathode segments of the additionalindicating unit 80 is designed to be smaller in area than that of thecathode segments of the other indicating units.

According to this embodiment, the same voltage should be supplied to thecathode segments of the additional indicating unit 80 and the cathodesegments of the indicating units 16a to 16p, however, the electriccurrent density in the cathode segment of the additional indicating unit80 is greater than that of the cathode segments of each of the otherindicating units 16a to 16p because the indicating area of theadditional indicating unit 80 is smaller than that of the indicatingunits 16a to 16p. 80 that the brightness of the additional indicatingunit 80 is greater than that of the indicating units 16a to 16p, it hasbeen found by way of example, that when the electric current density inthe cathode segment 81 of the additional indicating unit 80 was selectedto be 1.2 mA/mm its brightness was 300 foot-lamberts. In the same tube,the electric current density in the cathode segment 46 of the indicatingunit 16a was 600 mA/mm its brightness was 150 footlamberts.

As described above, the calculated information in the output circuits ofthe matrix 72 is displayed on all of or a part of the indicating units160 to 16p in the tube 10. If the results calculated in the matrix 72require more digits than available such, for example, 20 digits, it isimpossible to display all of the digits at one time on the indicatingunits 16a to 16p. That is, the tube as illustrated, is only able todisplay 16 digits, and four other digits are not displayed thereon.Under this set of circumstances, the predetermined required voltagesupplied between the anode and cathode segments of the additionalindicating unit 80 by the closing of its switch S,,, so that theadditional unit 80 will be energized. As is well-known, the additionalindicating unit 80 performs the so-called over-flow indication. Theoverflow indication is, as described above, brighter than the otherindications. An operator is thereby notified that the display indicationis an over-flow.

Further, all of the cathode segments 81 to 85 of the additionalindicating unit 80 may be energized to indicate an over-flow. It ispossible, however, to energize only segments 82, 83 and 85, or 81, 82,84 and 85, etc.

Further, it is possible to display a minus indication on the additionalindicating unit 80. In order to display this minus indication, thecathode segment 83 alone is energized. This minus indication is brighterthan the other indicating units, so that the operator is notified ofsuch mark.

FIG. 4 illustrates the face of a second embodiment of the presentinvention. In this embodiment, there are a plurality of standardindicating units 101a to 101g, an indicating unit 103 for amultiplication mark, a indicating unit 104 for an over-flow or minusmark, indicator units 105a to 105C for exponent numerals representingthe power to which the base 10 is to be raised, and an indicating unit106 for a minus sign to be used in front of the exponent numerals 105a,105b and 105( if it is to be the inverse power of the base 10. The aboveindicating units are all formed on a base of a tube 100. The indicatingarea of each cathode segment of the units 104, a to 1050 and 106 issmaller than that of the cathode segments of the other indicating units101a to 1013, 102 and 103. As used herein, the units 104, 105a to 105Cand 106 are termed additional indicating units, so that it will beunderstood that said brightness of the units 104, 105a to 1050 and 106are greater than that of the other units.

FIG. 5 shows a fragmentary schematic circuit diagram of some of theindicating units illustrated in FIG. 4. The indicating unit 101aconsists of seven cathode segments 111a to 117a having a conventionalfigure 8 formation. Additionally, there is a cathode segment 118a for adecimal point. Also, there is an anode segment 119a associated with thecathode segments 111a to 118a. Similarly, the indicating unit 1011)consists of seven cathode segments lllb to 1l7b formed as a figure 8, acathode segment 118b for a decimal point and an anode segment 11%associated with the cathode segments lllb to 118b. Further, the exponentindicating unit 105a consists of seven cathode segments 12111 to 1270,in a figure 8 configuration, a cathode segment 128a for a decimal pointand an anode segment 129a associated with the cathode segments 121a to128a. The exponent indicating unit l05b consists of seven cathodesegments 12112 to 127b, forming a figure 8, a cathode segment 128b andan anode segment 12% corresponding to all i of the cathode segments 121ato 128b.

In FIG. 5, each of the anode segments 119a to 12% of units 101a to l05bare connected to a source E through switches 131a to l4l b and a commonlead 150. The corresponding cathode segments, for example, a, 115b, aand l25b of each unit are connected to each other by a common lead 151,and also the corresponding cathode segments 116a to l26b of each unitare connected to each other by a common lead 152. The leads I51 and 152are grounded through resistances 151R and 152R and switches 1515 and152s, respectively. Further, it will be understood that the connectionof the other anode and cathode segments of the other units are arrangedin the same manner. The switches of anode segments and cathode segmentsare controlled by a calculator matrix 72' t cause desired indications.

According to this second embodiment, it is possible to indicate a numbercomposed of a number of digits multiplied by the base 10 raised to apower represented by an exponent composed of at least one digit such,for example, as 3.0621 X 10". For displaying said 3.0621 X 10", thestandard indicating units 1010 to 103 are energized to indicate 3.0621 X10, and indicating units 105b and 1050 are energized to indicate theexponent 12. In this case, the indicating areas of the cathode segmentsof the units lb and 1050 have been designed smaller than that of cathodesegments of the units 101C to I03, and hence the brightness of theexponents is greater. The operators attention is thus directly called tothe exponents. If an over-flow is contained, it may be displayed on theunit 104.

As shown in FIG. 5, a resistance 124R is connected between the cathodesegment 125a and the common lead 151. Similarly, a resistance 126R isconnected between the cathode segment 126a and common lead 152. Otherresistances are connected between each cathode segment of eachadditional indicating unit and the corresponding common leads. Suchresistances are formed on the base 100 when the indicating units areformed. As described above, the indicating area of each additionalindicating unit is very small, so that the current density is great, andhence the life of the additional indicating units would be shorter thanthat of the indicating units. However, by adding the resistance, thelife of the additional indicator unit may be extended. Of course, thevalue of the resistance should be selected so that the brightness of theadditional indicating unit is greater than that of the other units.These resistance elements may be omitted if full brightness is desired.

Although the invention has been described in connection with thepreferred embodiments, it is not to be so limited as changes andmodifications may be made which are within the full intended scope ofthe invention as defined by the appended claims.

I claim as my invention:

1. A gaseous glow indicator tube comprising a base plate of insulatingmaterial, a transparent cap sealed to said base plate and forming a gastight chamber therewith, an ionizing gas in said chamber, a sheet ofinsulating material within said chamber and disposed on said base plate,a plurality of main similarly segmented indicator units within saidchamber on the outer face of said sheet, each of said segmented unitsincluding a like number of cathode segments similarly located in apredetermined pattern in each indicator unit, at least one anode segmentforming a part of each indicator unit and each located on said insulatedsheet in the same plane as said cathode segments, a plurality ofenergizing leads on said insulating sheet corresponding in number to themaximum number of cathode segments in a single indicator unit, secondaryleads on the underside of said insulating sheet connected respectivelyto said cathode energizing leads; means connecting said secondary leadsto said cathode segments through said insulating sheet, at least oneanode energizing lead for each indicator unit, a secondary lead for eachindicator unit connecting the anodes of each indicator unit to an anodeenergizing lead respectively, a secondary indicator unit in said chamberincluding at least one cathode segment and one anode segment disposed onsaid insulating sheet, each cathode segment of said secondary indicatorunit being smaller in area than the area of any one of said cathodesegments of said main indicator units, an energizing lead for eachcathode segment of said secondary indicator unit located on said outerface of said insulating sheet, circuit connections between each of saidcathode energizing leads of said secondary indicator unit and associatedcathode segment, energizing leads for said anodes of said secondaryindicator units connected to their associated anodes respectively, andmeans for connecting successively said anode energizing circuits to apositive source of potential on a time sharing basis and simultaneouslyconnecting selected ones of said cathode segments of each indicator unitto the negative side of the same source of potential on the same timesharing basis, thereby to cause selected segments of each indicator unitto glow and in which there is provided a resistor element in eachcathode segment energizing circuit of said secondary indicator unit,thereby to reduce the current density in each such cathode segment whenenergized, the resistive value of each resistance element beingsufficient to reduce the glow of its associated cathode segment only toa point where the cathode segment is still brighter than the cathodesegments of said main indicator units.

2. A gaseous glow indicator tube according to claim 1 in which thecathode segments of each indicator unit are arranged in a figure 8pattern and in which the cathode segments of at least one secondaryindicator unit are arranged in a pattern to display an overflow.

3. A gaseous glow indicator tube according to claim 1 in which thecathode segments of each indicator unit are arranged in a figure 8pattern, and in which the cathode segments of at least one secondaryindicator unit are arranged in a pattern to display an exponent of anumber displayed by said main indicator units.

4. A gaseous glow indicator tube according to claim 1 in which thecathode segments of each indicator unit are arranged in a figure 8pattern and in which the cathode segments of at least one secondaryindicator unit are arranged in a pattern to display an overflow andother of said secondary indicator units are arranged in a pattern todisplay an exponent ofa number displayed by said main indicator units.

5. A gaseous glow indicator tube according to claim 1, in which at leastsome of said anode segments are U- shape with only a single such anodesegment for each indicator unit in which it is located.

6. A gaseous glow indicator tube according to claim 1, in which at leastone secondary indicator unit has five cathode segments arranged in afigure X configuration with four of such segments and having a cross barbetween and spaced from the inner ends of the legs of the X.

7. A gaseous glow indicator tube according to claim 1, in which at leastone secondary indicator unit has five cathode segments arranged in afigure X" configuration with four of such segments and having a crossbar between and spaced from the inner ends of the legs of the X", and inwhich six anode segments are positioned around the cathode segments andin the same plane.

8. A gaseous glow indicator tube according to claim 1 in which eachindicator unit is formed on an insulating layer covered by a transparentcover, and each resistive element is formed on said insulating layer.

9. A gaseous glow indicator tube comprising a plurality of indicatorunits of one type each of which includes at least one anode and aplurality of cathode segments arranged in a figure 8 configuration, saidanode and said cathode segments all lying in a common plane, at leastone additional second type indicator unit each including at least oneanode and a plurality of cathode segments arranged in a figure 8configuration and positioned to represent a power of a number displayedby cathode segments of said one type indicator unit, each cathodesegment of said second type indicator unit being smaller in area thanthe area of any one of the cathode segments of said one type indicatorunit. a

tor units of said third type, and in which there is provided a resistorelement in each cathode segment energizing circuit of said second typeindicator unit, thereby to reduce the current density in each suchcathode segment when energized, the resistive value of each resistanceelement being sufficient to reduce the glow of its associated cathodesegment only to a point where the cathode segment is still brighter thanthe cathode segments of said one type indicator unit.

1. A gaseous glow indicator tube comprising a base plate of insulatingmaterial, a transparent cap sealed to said base plate and forming a gastight chamber therewith, an ionizing gas in said chamber, a sheet ofinsulating material within said chamber and disposed on said base plate,a plurality of main similarly segmented indicator units within saidchamber on the outer face of said sheet, each of said segmented unitsincluding a like number of cathode segments similarly located in apredetermined pattern in each indicator unit, at least one anode segmentforming a part of each indicator unit and each located on said insulatedsheet in the same plane as said cathode segments, a plurality ofenergizing leads on said insulating sheet corresponding in number to themaximum number of cathode segments in a single indicator unit, secondaryleads on the underside of said insulating sheet connected respectivelyto said cathode energizing leads; means connecting said secondary leadsto said cathode segments through said insulating sheet, at least oneanode energizing lead for each indicator unit, a secondary lead for eachindicator unit connecting the anodes of each indicator unit to an anodeenergizing lead respectively, a secondary indicator unit in said chamberincluding at least one cathode segment and one anode segment disposed onsaid insulating sheet, each cathode segment of said secondary indicatorunit being smaller in area than the area of any one of said cathodesegments of said main indicator units, an energizing lead for eachcathode segment of said secondary indicator unit located on said outerface of said insulating sheet, circuit connections between each of saidcathode energizing leads of said secondary indicator unit and associatedcathode segment, energizing leads for said anodes of said secondaryindicator units connected to their associated anodes respectively, andmeans for connecting successively said anode energizing circuits to apositive source of potential on a time sharing basis and simultaneouslyconnecting selected ones of said cathode segments of each indicator unitto the negative side of the same source of potential on the same timesharing basis, thereby to cause selected segments of each indicator unitto glow and in which there is provided a resistor element in eachcathode segment energizing circuit of said secondary indicator unit,thereby to reduce the current density in each such cathode segment whenenergized, the resistive value of each resistance element beingsufficient to reduce the glow of its associated cathode segment only toa point where the cathode segment is still brighter than the cathodesegments of said main indicator units.
 2. A gaseous glow indicator tubeaccording to claim 1 in which the cathode segments of each indicatorunit are arranged in a figure 8 pattern and in which the cathodesegments of at least one secondary indicator unit are arranged in apattern to display an overflow.
 3. A gaseous glow indicator tubeaccording to claim 1 in which the cathode segments of each indicatorunit are arranged in a figure ''''8'''' pattern, and in which thecathode segments of at least one secondary indicator unit are arrangedin a pattern to display an exponent of a number displayed by said mainindicator units.
 4. A gaseous glow indicator tube according to claim 1in which the cathode segments of each indicator unit are arranged in afigure 8 pattern and in which the cathode segments of at least onesecondary indicator unit are arranged in a pattern to display anoverflow and other of said secondary indicator units are arranged in apattern to display an exponent of a number displayed by said mainindicator units.
 5. A gaseous glow indicator tube according to claim 1,in which at least some of said anode segments are U-shape with only asingle such anode segment for each indicator unit in which it Islocated.
 6. A gaseous glow indicator tube according to claim 1, in whichat least one secondary indicator unit has five cathode segments arrangedin a figure X configuration with four of such segments and having across bar between and spaced from the inner ends of the legs of the X.7. A gaseous glow indicator tube according to claim 1, in which at leastone secondary indicator unit has five cathode segments arranged in afigure ''''X'''' configuration with four of such segments and having across bar between and spaced from the inner ends of the legs of the''''X'''', and in which six anode segments are positioned around thecathode segments and in the same plane.
 8. A gaseous glow indicator tubeaccording to claim 1 in which each indicator unit is formed on aninsulating layer covered by a transparent cover, and each resistiveelement is formed on said insulating layer.
 9. A gaseous glow indicatortube comprising a plurality of indicator units of one type each of whichincludes at least one anode and a plurality of cathode segments arrangedin a figure 8 configuration, said anode and said cathode segments alllying in a common plane, at least one additional second type indicatorunit each including at least one anode and a plurality of cathodesegments arranged in a figure 8 configuration and positioned torepresent a power of a number displayed by cathode segments of said onetype indicator unit, each cathode segment of said second type indicatorunit being smaller in area than the area of any one of the cathodesegments of said one type indicator unit, a transparent envelopeenclosing said indicator units and an ionizing gas in said envelope andmeans for selectively energizing said indicator units of said one typeand said second type, further including an indicator unit of a thirdtype which includes at least one anode and at least one cathode segmentarranged to display a mathematical function, each cathode segment ofsaid third type indicator unit being smaller in area than any one of thecathode segments of said first type indicator units and means forselectively energizing said indicator units of said third type, and inwhich there is provided a resistor element in each cathode segmentenergizing circuit of said second type indicator unit, thereby to reducethe current density in each such cathode segment when energized, theresistive value of each resistance element being sufficient to reducethe glow of its associated cathode segment only to a point where thecathode segment is still brighter than the cathode segments of said onetype indicator unit.